/*
navbar
*/
let lis = document.querySelectorAll('a')
            let page01 = document.getElementById('page01')
            let page02 = document.getElementById('page02')
            let page03 = document.getElementById('page03')
            let page04 = document.getElementById('page04')
            let page05 = document.getElementById('page05')
            for (let i = 0; i < lis.length; i++) {
                lis[i].onclick = function(event){
                        if(event.target.classList.contains('first')){
                            changPage()
                            page01.style.display = 'block'
                        }else if(event.target.classList.contains('second')){
                            changPage()
                            page02.style.display = 'block'
                        }else if(event.target.classList.contains('third')){
                            changPage()
                            page03.style.display = 'block'
                        }else if(event.target.classList.contains('forth')){
                            changPage()
                            page04.style.display = 'block'
                        }
                    }
                    
                }
             
            
            function changPage(){
                
                document.querySelectorAll('.page').forEach(el=>{
                    el.style.display = 'none'
                })
            }